1. Field of the Invention
The present invention relates to a surface acoustic wave device that comprises a chip on which a spiral inductor is formed.
2. Description of the Related Art
A surface acoustic wave device is employed in high-frequency circuit components of cellular phones or other miniature wireless devices, such as in splitters (duplexers) that are connected to a transmission/reception common antenna, for example. In this case, a surface acoustic wave device is constituted such that a SAW filter, which uses a surface acoustic wave element, and a phase shift circuit for separating the transmission and reception frequency bands or a phase matching circuit are mounted in a common package for the sake of miniaturization.
Proposals for further miniaturizing and shortening the height of such a surface acoustic wave device and a variety of proposals for enhancing the characteristics of the phase shift circuit or phase matching circuit to be used in the splitter have been made (Japanese Patent Application Laid Open Nos. H10-126213, 2001-127588, and H8-32402, for example).
The invention that appears in Japanese Patent Application Laid Open No. H10-126213 forms a phase matching circuit in a multilayered structure and implements miniaturization of the splitter by means of a SAW filter cavity structure that is mounted on the multilayered structure. Further, the invention in Japanese Patent Application Laid Open No. 2001-127588 proposes a structure in which an integrated circuit element is mounted on an upper substrate on the opposite side to the base substrate that does not meet the demands to facilitate fabrication and afford additional miniaturization and shortening of conventional structures in which two transmission/reception filters and an integrated circuit element that constitutes a peripheral circuit such as a phase matching circuit are commonly disposed on a base substrate.
In addition, the invention that appears in Japanese Patent Application Laid Open No. H8-32402 provides a solution for the occurrence of a characteristic variation that is caused by a parasitic capacitance produced between the surface of a matching inductance substrate and the lid of the package and for the generation of loss deterioration in a structure in which the surface acoustic wave element and matching inductance are stored in the same package. Therefore, the parasitic capacitance is suppressed by separating the mounted lid and the surface of the matching inductance substrate housed in the package by a distance of 0.5 mm or more.
In the process of examining additional miniaturization and shortening of a surface acoustic wave device that comprises a chip on which a spiral inductor is formed, the present inventors discovered that, in the case of a constitution in which a chip on which a spiral inductor is formed is flip-chip mounted on a cavity substrate face, the influence on the inductance value and performance index (Q value) of the spiral inductor of the distance of the metal (conductor) pattern disposed on the cavity-substrate face facing the spiral inductor and the amount of overlap of the metal (conductor) pattern and therefore discovered a specific distance for the metal (conductor) pattern disposed on the cavity substrate face and a specific amount for the overlap with the metal (conductor) pattern in order to obtain the preferred characteristics.